如何在android-navigation lib上隐藏BottomNavigationView

Question

我试图在我的APP中使用android-navigation lib，并且按照教程中的说明进行操作。我只想在我的APP中使用一个活动。我对一个问题感到困惑。有些片段只是不想要BottomNavigationView，我怎么藏起来 这是我的main_layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:elevation="0dp"
        android:theme="@style/AppTheme.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="?attr/actionBarSize"
            android:fitsSystemWindows="true"
            app:popupTheme="@style/AppTheme.PopupOverlay" >

        </androidx.appcompat.widget.Toolbar>

    </com.google.android.material.appbar.AppBarLayout>

    <fragment
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        app:defaultNavHost="true"
        app:navGraph="@navigation/carkeeper_navigation"/>

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/menu_bottom_nav"
    app:itemTextColor="@color/bottom_nav_title_color_selector"
    app:itemIconSize="@dimen/x40"
    app:menu="@menu/menu_main_bottom_nav"
    app:labelVisibilityMode="labeled">

</com.google.android.material.bottomnavigation.BottomNavigationView>

这是我的主要活动

class MainActivity : BaseActivity() {

private lateinit var navController: NavController
private lateinit var bottomNavigationView: BottomNavigationView
private lateinit var appBarConfiguration: AppBarConfiguration

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.home_activity)

    navController = Navigation.findNavController(this, R.id.nav_host_fragment)
    appBarConfiguration = AppBarConfiguration(navController.graph, null)
    setSupportActionBar(findViewById(R.id.toolbar))

    bottomNavigationView = findViewById(R.id.menu_bottom_nav)
    bottomNavigationView.setupWithNavController(navController)
    bottomNavigationView.itemIconTintList = null
}}

然后是navigaton_graph

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/carkeeper_navigation"
app:startDestination="@id/mainFragment">

<fragment
    android:id="@+id/mainFragment"
    android:name="com.saicfinance.carkeeper.func.main.MainFragment"
    android:label="MainFragment"
    tools:layout="@layout/home_fragment">
</fragment>

<fragment
    android:id="@+id/mineFragment"
    android:name="com.saicfinance.carkeeper.func.mine.MineFragment"
    android:label="@string/mine_title"
    tools:layout="@layout/mine_fragment" >

    <action android:id="@+id/action_mine_fragment_to_setting_fragment"
        app:destination="@id/settingFragment"
        app:enterAnim="@anim/slide_in_right"
        app:exitAnim="@anim/slide_out_left"
        app:popEnterAnim="@anim/slide_in_left"
        app:popExitAnim="@anim/slide_out_right"/>
</fragment>

<fragment
    android:id="@+id/settingFragment"
    android:name="com.freddy.func.setting.SettingFragment"
    android:label="setting_fragment"
    tools:layout="@layout/setting_fragment" />

我知道我可以将BottomNavigationView设置为导航到settingFragment时消失。然后将BottomNavigationView设置为可见时可见，但这很奇怪。任何可以帮助我的人，在此先感谢。

Answer 1

Android 官方网站上有一个解决方案：

https://developer.android.com/guide/navigation/navigation-ui

navController.addOnDestinationChangedListener { _, destination, _ ->
   if(destination.id == R.id.full_screen_destination) {
      toolbar.visibility = View.GONE
      bottomNavigationView.visibility = View.GONE
   } else {
      toolbar.visibility = View.VISIBLE
      bottomNavigationView.visibility = View.VISIBLE
   }
}

Answer 2

您可以在活动的onCreate中执行类似的操作。一旦在导航栏中选择了一项，它将根据片段ID显示或隐藏导航。

private fun setupNav() {
    val navController = findNavController(R.id.nav_host_fragment)
    findViewById<BottomNavigationView>(R.id.bottomNav)
        .setupWithNavController(navController)

    navController.addOnDestinationChangedListener { _, destination, _ ->
        when (destination.id) {
            R.id.mainFragment -> showBottomNav()
            R.id.mineFragment -> showBottomNav()
            else -> hideBottomNav()
        }
    }
}

private fun showBottomNav() {
    bottomNav.visibility = View.VISIBLE

}

private fun hideBottomNav() {
    bottomNav.visibility = View.GONE

}

Answer 3

接受的答案有效，它是官方文档中推荐的答案，但正如评论中所述，它确实会导致一些闪烁，因为在附加片段之前执行回调。

我发现以下答案更灵活，并且可以更好地处理动画：

supportFragmentManager.registerFragmentLifecycleCallbacks(object : FragmentManager.FragmentLifecycleCallbacks() {
        override fun onFragmentViewCreated(fm: FragmentManager, f: Fragment, v: View, savedInstanceState: Bundle?) {
            TransitionManager.beginDelayedTransition(binding.root, Slide(Gravity.BOTTOM).excludeTarget(R.id.nav_host_fragment, true))
            when (f) {
                is ModalFragment -> {
                    binding.bottomNavigation.visibility = View.GONE
                }
                else -> {
                    binding.bottomNavigation.visibility = View.VISIBLE
                }
            }
        }
    }, true)

您可以根据片段之间的转换，通过选择不同的动画（在我的示例中是幻灯片）或通过在另一个生命周期回调中进行调用来自定义它。

Answer 4

@Samuel Grogan 的回答是正确的，但是如果您遇到底部导航在设备旋转时意外显示/隐藏的问题，您可以使用 ViewModel 来解决此问题：

主视图模型

class MainViewModel : ViewModel() {

    private val _bottomNavigationVisibility = MutableLiveData<Int>()
    val bottomNavigationVisibility: LiveData<Int>
        get() = _bottomNavigationVisibility

    init {
        showBottomNav()
    }

    fun showBottomNav() {
        _bottomNavigationVisibility.postValue(View.VISIBLE)
    }

    fun hideBottomNav() {
        _bottomNavigationVisibility.postValue(View.GONE)
    }
}

主要活动

class MainActivity : AppCompatActivity() {
    private lateinit var mainViewModel: MainViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        mainViewModel = ViewModelProvider(this).get(MainViewModel::class.java)
        val bottomNav: BottomNavigationView = findViewById(R.id.nav_view)

        val navController = findNavController(R.id.nav_host_fragment)
        bottomNav.setupWithNavController(navController)

        mainViewModel.bottomNavigationVisibility.observe(this, Observer { navVisibility ->
            bottomNav.visibility = navVisibility
        })

        navController.addOnDestinationChangedListener { _, destination, _ ->
            when (destination.id) {
                R.id.comment_fragment -> mainViewModel.hideBottomNav()
                else -> mainViewModel.showBottomNav()
            }
        }
    }
}